Photographic silver halide emulsions containing thioether derivatives as antifoggants and stabilizers



United States Patent PHOTOGRAPHIC SILVER HALIDE EMULSIONS CONTAINING THIOETHER DERIVATIVES AS ANTIFOGGANTS AND STABILIZERS Arthur H. Her-z and Norman W. Kalenda, both of Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey N0 Drawing. Filed Aug. 25, 1961, Ser. No. 133,768

18 Claims. (CI. 9661) This invention relates to photographic compositions. Preferred embodiments of the invention concern photographic silver halide emulsions containing certain mercapto derivatives that can serve as fog-inhibiting agents or as stabliizing agents obviating the necessity of conventional fixing.

It is well known that photographic silver halide emulsions on storage tend to lose sensitivity and to become spontaneously developable without exposure to light. There is normally a detectable amount of the silver salt reduced during development in the areas where no exposure was given, this being commonly called fog and sometimes chemical fog where it is necessary to distinguish between it and the effects of accidental exposure to radiation. Fog tends to increase on storage for extended periods of time, particularly under elevated temperatures and humidities such as prevail during thte summer months and in the tropics. It is thus desirable to have a method for minimizing such fog formation.

After a photographic silver halide emulsion is developed and a silver image is produced in the areas of exposure, the silver halide in the unexposed areas is conventionally washed out as a soluble complex with a fixing solution. It would be convenient to have the fixing agent incorporated directly in the emulsion. However, usual fixing agents are not suitable for incorporation directly in emulsions as they form complexes with silver halide regardless of the acidity of the environment. Also many fixing agents would cause substantial desensitization of the emulsion if incorporated therein. It is thus desirable to have 'fixing materials that are sufiiciently compatible with photographic silver halide emulsions so that they can be utilized therein.

It is an object of this invention to provide a new class of photographic emulsion addenda.

It is another object of this invention to provide novel photographic silver halide emulsions inhibited against fog formation.

It is still another object of this invention to provide novel photographic silver halide emulsions that can be processed without the use of a conventional fixing or stabilizing step.

These and other objects of the invention can be accomplished by photographic silver halide emulsions having incorporated therein sulfur-containing derivatives having either the formula can be represented by the formula 3,140,178 Patented July 7, 1964 wherein Y is a hydrogen atom, a nitro radical, an alkoxy radical (OR), an acyl radical a tertiary amino radical and others, with R and R being alkyl radicals having 1 to 20 and preferably 1 to 4 carbon atoms. The thioether radical for the substituent X can be represented by the formula -SZ wherein Z represents an organic radical such as an aryl radical, an aralkyl radical, a substituted alkyl radical, a heterocyclic radical or the like. Typical thioether radicals include such radicals as:

wherein R is a carboxyl radical, an amino radical or an alkyl radical generally having 1 to 20 and preferably 1 to 4 carbon atoms;

wherein n is an integer of 1 to 10 and preferably 1 to 4 and wherein R is the same as described above;

wherein R is an alkylene radical having 1 to 20 and preferably 1 to 4 carbn atoms and M is an amide radical, a sulfonyl radical, a hydroxyl radical, an alkoxy radical, an amino radical, an ester radical, a carboxyl radical or a heterocyclic radical such as a morpholino radical; or a heterocyclic organic radical such as a phenyl tetrazine radical, a morpholino radical or the like. Illustrative alkyl radicals for the above substituents include methyl, ethyl, n-butyl, Z-ethylhexyl, n-decyl, n-dodecyl, stearyl, eicosyl etc. as well as analogous alkylene radicals for the alkylene substituents.

The above-described emulsion addenda can be readily prepared by well-known techniques (cf. B. H. Nicholet, J.A.C.S. 53, 3066, 1931).

The addenda having the structure of Formula A above are B-aminosulfides that can be readily prepared by reacting thiols and Schiif bases such as azamethines as described in Stacy et al., J.A.C.S., 77, 3869, 1955 and which can be represented by the following equation to prepare a typical thioether derivative addenda of the invention by reacting p-thiocresol and benzalaniline:

The addenda having the structure of Formula B above are Michael adducts that can be readily prepared by reacting thiols and unsaturated compounds having an activating proton substituent as described in Tarbell and Harnish, Chem. Rev., 49, 23, 1951, and which can be represented by the following equation to prepare a typical thioether derivative or addenda of the invention by reacting mercapto pivalic acid and chalcone:

S-CHr-(f-C OH The feature addenda of the invention can be utilized in photographic silver halide emulsions to serve as antifoggants. These addenda serve to stabilize emulsions under prolonged storage conditions or under conditions of high temperature and humidity which typically occur in tropical climates. The amount of the subject addenda that is used in photographic silver halide emulsions for antifoggant purposes can be varied in accordance with usual practice, the amount utilized varying with the effect desired, degree of ripening, silver content of the emulsion, etc. Generally from about .001 to grams of addenda per mole of silver halide are suitable for antifoggant purposes.

The photographic silver halide emulsion addenda of the invention can also serve as incorporated fixing agents. These addenda do not prevent development of exposed areas of the emulsion but protect the unexposed areas of the emulsion against print out after development of the emulsion. Thus with emulsions containing the addenda of the invention, silver images can be formed and stabilized without the use of a conventional fixing process. The subject addenda are stable and do not act as fixing agents in acidic or neutral media such as in emulsions. However, under aqueous alkaline conditions, such as prevail during the developing of photographic emulsions, the subject addenda become active fixing agents. Under such conditions a complex is formed with the silver halide in the unexposed and undeveloped areas of the emulsion, and which complex is more stable than silver halide to light, atmosphere and reducing conditions and which complex does not decompose to silver or silver sulfides. When the subject addenda are used in photographic silver halide emulsions as image stabilizing or fixing agents, at least one mole of the addenda is utilized for each mole of silver halide in the emulsion.

The preparation of photographic silver halide emulsions such as are used with the addenda of this invention involves three separate operations: (1) emulsification and digestion of silver halide, (2) the freeing of the emulsion of excess water-soluble salts, suitably by washing with water, and (3) the second digestion or afterripening to obtain increased emulsion speed or sensitivity. (Mees, The Theory of the Photographic Process, 1954.) The addenda of the invention can be added to the emulsion before the final digestion or after-ripening, or they can be added immediately prior to the coating.

The addenda of the invention can be added to photo graphic emulsions using any of the well-known techniques in emulsion making. For example, they can be dissolved in a suitable solvent and added to the silver halide emulsion, or they can be added to the emulsion in the form of a dispersion similar to the technique used to in corporate certain types of color-forming compounds (couplers) in a photographic emulsion. Techniques of this type are described in Jelley et al. U.S. Patent 2,322,- 027, issued June 15, 1943, and Fierke et al. U.S. Patent 2,801,171, issued July 30, 1957. The solvent should be selected so that it has no harmful effect upon the emulsion in accordance with usual practice, and generally solvents or diluents which are miscible with water are to be preferred.

The emulsions of the invention can be chemically sensitized by any of the other well-known procedures. The

emulsions can be digested with naturally active gelatin, or sulfur compounds can be added, such as those described in Sheppard U.S. Patent 1,574,944, issued March 2, 1926, and Sheppard et al. 1,623,499, issued April 5, 1927, and Sheppard and Brigham U.S. Patent 2,410,689, issued November 5, 1946. The emulsions can also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum. Representative compounds are ammonium chloropalladate, potassium chloroplatinate, and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U.S. Patent 2,448,060, issued August 31, 1948, and as antifoggants in higher amounts, as described in Trivelli and Smith U.S. Patents 2,566,245, issued August 28, 1951, and 2,566,263, issued August 28, 1951. The emulsions can also contain sensitizing amounts of gold salts as described in Waller et al. U.S. Patent 2,399,- 083, issued April 23, 1946, or stabilizing amounts of gold salts as described in Damschroder U.S. Patent 2,597,- 856, issued May 27, 1952, and Yutzy and Leermakers U.S. Patent 2,597,915, issued May 27, 1952. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride. The emulsions can also contain sensitizing amounts of reducing agents such as stannous salts (Carroll U.S. Patent 2,487,850, issued November 15, 1949), polyamines, such as diethylene triamine (Lowe and Jones U.S. Patent 2,518,698, issued August 15, 1950), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925, issued September 12, 1950), or bis(B-aminoethyl)sulfide and its watersoluble salts (Lowe and Jones U.S. Patent 2,521,926, issued September 12, 1950).

The emulsions can also be optically sensitized with cyanine and merocyanine dyes, such as those described in Brooker U.S. Patents 1,846,301, issued February 23, 1932; 1,846,302, issued February 23, 1932; and 1,942,- 854, issued January 9, 1934; White U.S. Patent 1,990,507, issued February 12, 1935; Brooker and White U.S. Patents 2,112,140, issued March 22, 1938; 2,165,338, issued July 11, 1939; 2,493,747 issued January 10, 1950; and 2,739,964, issued March 27, 1956; Brooker and Keyes U.S. Patent 2,493,748, issued January 10, 1950; Sprague U.S. Patents 2,503,776, issued April 11, 1950 and 2,519,- 001, issued August 15, 1950; Heseltine and Brooker U.S. Patent 2,666,761, issued January 19, 1954; Heseltine U.S. Patent 2,734,900, issued February 14, 1956; VanLare U.S. Patent 2,739,149, issued March 20, 1956; and Kodak Limited British Patent 450,958, accepted July 15, 1936.

The emulsions of the invention can also contain such stabilizing compounds as the mercury compounds of Allen, Byers, and Murray U.S. Patent 2,728,663, issued December 27, 1955; Carroll and Murray U.S. Patent 2,728,664, issued December 27, 1955; and Leubner and Murray U.S. Patent 2,728,665, issued December 27, 1955; the triazoles of Heimbach and Kelly U.S. Patent 2,444,608, issued July 6, 1948; the azaindenes of Heimbach and Kelly U.S. Patents 2,444,605 and 2,444,606, issued July 6, 1948; Heimbach U.S. Patents 2,444,607, issued July 6, 1948 and 2,450,397, issued September 28, 1948; Heimbach and Clark U.S. Patent 2,444,609, issued July 6, 1948; Allen and Reynolds U.S. Patents 2,713,541, issued July 19, 1955 and 2,743,181, issued April 24, 1956; Carroll and Beach U.S. Patent 2,716,062, issued August 23, 1955; Allen and Beilfuss U.S. Patent 2,735,769, issued February 21, 1956; Reynolds and Sagal U.S. Patent 2,756,147, issued July 24, 1956; Allen and Sagura U.S. Patent 2,772,164, issued November 27, 1956, and those disclosed by Birr in Z. wiss. Phot., vol. 47, 1952, pages 228; the quaternary benzothiazolium compounds of Brooker and Stand U.S. Patent 2,131,038, issued September 27, 1938; the disulfides of Kodak Belgian Patent 569,- 317, granted July 31, 1958; and the zinc and cadmium salts of Jones U.S. Patent 2,839,405, issued June 17, 1958.

The emulsions can also contain speed-increasing compounds of the quaternary ammonium type of Carroll U.S. Patent 2,271,623, issued February 3, 1942; Carroll and Allen U.S. Patent 2,288,226, issued June 30, 1942; and Carroll and Spence U.S. Patent 2,334,864, issued November 23, 1943; and the polyethylene glycol type of Carroll and Beach U.S. Patent 2,708,162, issued May 10, 1955.

The emulsion can contain a suitable gelatin plasticizer such as glycerin; a dihydroxy alkane such as 1,5-pentane diol as described in Milton and Murray U.S. Patent 2,960,404, issued November 15, 1960; an ester of an ethylene bis-glycolic acid such as ethylene bis(methyl glycolate) as described in Milton U.S. Patent 2,904,434, issued September 15, 1959; bis(ethoxy diethylene glycol) succinate as described in Gray U.S. Patent 2,940,854, issued June 14, 1960, or a polymeric hydrosol as results from the emulsion polymerization of a mixture of an amide of an acid of the acrylic acid series, an acrylic acid ester and a styrene-type compound as described in Tong U.S. Patent 2,852,386 issued September 16, 1958. The plasticizer may be added to the emulsion before or after the addition of a sensitizing dye, if used.

The emulsion can be hardened with any suitable hardener for gelatin such as formaldehyde; a halogen-substituted aliphatic acid such as mucobromic acid as described in White U.S. Patent 2,080,019, issued May 11, 1937; a compound having a plurality of acid anhydride groups such as 7,8-diphenylbicyclo(2,2,2)-7-octene-2,3,5,6-tetracarboxylic dianhydride, or a dicarboxylic or a disulfonic acid chloride such as terepht haloyl chloride or naphthalene-1,5-disulfonyl chloride as described in Allen and Carroll U.S. Patents 2,725,294 and 2,725,295, both issued November 29, 1955; a cyclic 1,2-diketone such as cyclopentane-1,2-dione as described in Allen and Byers U.S. Patent 2,725,305, issued November 29, 1955; a bisester of methane-sulfonic acid such as 1,2-di-(methanesulfonoxy)ethane as described in Allen and Laakso US. Patent 2,726,162, issued December 6, 1955; 1,3-dihydroxymethylbenzimidazol-Z-one as described in July, Knott and Pollak U.S. Patent 2,732,316, issued January 24, 1956; a dialdehyde or a sodium bisulfite derivative thereof, the aldehyde groups of which are separated by 2-3 carbon atoms, such as fi-methylglutaraldehyde bissodium bisulfite; a bisaziridine carboxamide such as trimethylene bis(1-aziridine carboxamide) as described in Allen and Webster U.S. Patent 2,950,197, issued August 23, 1960; or 2,3-dihydroxy dioxane as described in Jetfreys U.S. Patent 2,870,013, issued January 20, 1959.

The emulsions can contain a coating aid such as saponin; a lauryl or oleoyl monoether of polyethylene glycol as described in Knox and Davis U.S. Patent 2,831,766, issued April 22, 1958; a salt of a sulfated and alkylated polyethylene glycol ether as described in Knox and Davis U.S. Patent 2,719,087, issued September 27, 1955; an acylated alkyl taurine such as the sodium salt of N-oleoyl-N-methyl taurine as described in Knox, Twardokus and Davis U.S. Patent 2,739,891, issued March 27, 1956; the reaction product of a dianhydride of tetracarboxybutane with an alcohol or an aliphatic amine containing from 8 to 18 carbon atoms which is treated with a base, for example, the sodium salt of the monoester of tetracarboxybutane as described in Knox, Stenberg and Wilson U.S. Patent 2,843,487, issued July 15, 1958; a water-soluble maleopimarate or a mixture of a water-soluble maleopimarate and a substituted glutamate salt as described in Knox and Fowler U.S. Patent 2,823,123, issued February 11, 1958; an alkali metal salt of a substituted amino acid such as disodium N-(carbop-tert. octylphenoxypentaethoxy)glutamate, or a sulfosuccinarnate such as tetrasodium N-(l,2-dicarboxyethyD-N-octadecyl sulfosuccinamate, or N-lauryl disodium sulfosuccinamate.

The thioether addenda of the invention can be used in various kinds of photographic emulsions. In addition to being useful in orthochromatic, panchromatic, and infrared sensitive emulsions, they are also useful in X-ray and other non-optically sensitized emulsions. They can be added to the emulsion before or after any optical sensitizing dyes which may be used. Various silver salts can be used as the sensitive salt such as silver bromide, silver iodide, silver chloride, or mixed silver halides such as silver chlorobromide or silver bromoiodide. The subject addenda can be used in emulsions intended for color photography, for example, emulsions containing colorforming couplers or emulsions to be developed by solutions containing couplers or other colopgenerating materials, emulsions of the mixed-packet type, such as described in Godowsky U.S. Patent 2,698,794, issued January 4, 1 955, or emulsions of the mixed-grain type, such as described in Carroll and Hanson U.S. Patent 2,592,243, issued April 8, 1952. Development accelerators can be utilized in developing such color emulsions including polyethylene glycols, their ester derivatives, their ether derivatives typically having the formula RO(CH CH O) H wherein R is an alkyl radical having 1 to 5 carbon atoms and wherein n is 15-100, and related derivatives. The subject addenda can also be used in emulsions which form latent images predominantly on the surface of the silver halide crystal or in emulsions which form latent images predominantly inside the silver halide crystal, such as those described in Davey and Knott U.S. Patent 2,592,250, issued April 8, 1952.

The subject addenda can also be used in emulsions intended for use in diifusion transfer processes which utilize the undeveloped silver halide in the non-image areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a receiving layer in close proximity to the original silver halide emulsion layer. Such processes are described in Rott U.S. Patent 2,352,014, issued June 20, 1944; and Land U.S. Patents 2,584,029, issued January 29, 1952; 2,608,236, issued December 28, 1954 and 2,543,181, issued February 27, 1951. They can also be used in color transfer processes which utilize the diifusion transfer of an imagewise distribution of developer, coupler or dye, from a lightsensitive layer to a second layer, while the two layers are in close proximity to one another. Color processes of this type are described in Land U.S. Patents 2,559,643, issued July 10, 1951 and 2,698,798, issued January 4, 1955; Land and Rogers Belgian Patents 554,933 and 554,934, granted August 12, 1957; International Polaroid Belgian Patents 554,212, granted July 16, 1957 and 554,935, granted August 12, 1957 and Yutzy U.S. Patent 2,756,- 142, issued July 24, 1956.

In the preparation of the silver halide dispersions employed for preparing silver halide emulsions, there can be employed as the dispersing agent for the silver halide in its preparation, gelatin or some other colloidal ma terial such as colloidal albumin, a cellulose derivative, or a synthetic resin, for instance, a polyvinyl compound, although gelatin is preferred. Some colloids which can be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in Lowe U.S. Patent 2,286,215, issued June 16, 1942; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 19- 26% as described in U.S. Patent 2,327,808 of Lowe and Clark, issued August 24, 1943; a water-soluble ethanol amine cellulose acetate as described in Yutzy U.S. Patent 2,322,085, issued June 15, 1943; a polyacrylamide having a combined acrylamide content of 3060% and a specific viscosity of 025-15 on an imidized polyacrylamide of like acrylamide content and viscosity as described in Lowe, Minsk and Kenyon U.S. Patent 2,541,474, issued February 13, 1951; zein as described in Lowe U.S. Patent 2,563,791, issued August 7, 1951; a vinyl alcohol polymer containing urethane carboxylic acid groups of the type described in Unruh and Smith U.S. Patent 2,768,154, issued October 23, 1956; or containing cyano-acetyl groups such as the vinyl alcohol-vinyl cyanoacetate copolymer as described in Unruh, Smith and Priest US. Patent 2,808,331, issued October 1, 1957; or a polymeric material which results from polymerizing a protein or a saturated acylated protein with a monomer having a vinyl group as described in Illingsworth, Dann and Gates US. Patent 2,852,382, issued September 19, 1958. If desired, compatible mixtures of two or more of these colloids can be employed for dispersing the silver halide in its preparation.

The above-described emulsions of the invention can be coated on a Wide variety of supports in accordance with usual practice. Typical supports for photographic elements of the invention include cellulose nitrate film, cellulose acetate film, polyvinyl acetal film, polystyrene film, polyethyleneterephthalate film and related films of resinous materials, as well as glass, paper, wood, metals and others.

The invention is further illustrated by the following examples of preferred embodiments thereof.

Several thioether addenda of the invention were prepared by the prior art methods described above, incorporated into photographic silver halide emulsions at varying concentrations and thereafter tested as antifoggants or as fixing agents. The structural formulas of these prepared addenda of the invention are numbered and listed below, the numbers given the addenda below being used to indicate these addenda in the tables or examples hereinafter. 1

Structural Formula Addenda CH3 SCHr-CCOH Addenda Structural Formula ll @p- -Q SQ HOG CHgCHg S-CHzillOH EXAMPLE 1 weeks, storage at 120 F. and a relative humidity of 50%, and in the form of film strips in an Eastman Type 1-B sensitometer, developed for 4 minutes at 68 F., and then fixed, washed and dried in the usual manner. Test samples containing no mercapto addenda of the invention were also included in the tests for purposes of comparison. The developer had the following formula:

N-methyl-p-aminophenol sulfate 2 Hydroquinone 8 Sodium sulfite (anhydrous) 90 Sodium carbonate monohydrate 52.5 Potassium bromide 5 Water to make one liter.

The results of the sensitometric tests are summarized by the data set out in Tables A and B below. In Tables A and B the speeds indicated are a function of the exposure necessary to give a density of 0.3 above background fog and expressed as a reciprocal relation to exposure, the initial control speed being taken as 100 in each case. The feature addenda in the tables correspond in number tothe formulas set out above. The concentrations of addenda are indicated in the tables as grams of addenda per mole of silver halide in the emulsion.

Table A Original Test 2 Weeks at 120 Cone. of F., 50% R.H. Addenda Addenda Speed '7 Fog Speed '7 Fog Table B 2 Weeks Original Test at 120 F., Addenda Cone. of 50% R.H.

Addenda Speed 7 Fog Fog Control. 100 72 .10 .36 Addendum #3---" .23 73 57 .08 .17 Addendum #4 .24 102 89 .11 .25 D0 96 80 .75 06 .21

As can be observed from the data set out in the above tables, the addenda of the invention impart substantial antifoggant properties to photographic silver halide emulsions.

EXAMPLE 2 N-methyl-p-aminophenol sulfate 2.5 Hydroquinone 8 Sodium sulfite (anhydrous) 30 Sodium borate 10 Potassium bromide Water to make one liter.

The results of the sensitome'tric tests are summarized by the data set out in Table C below wherein the speeds and concentration units are as described for Tables A and B.

The determination of the antifoggant properties of several additional addenda of the invention was carried out by the general procedure described in Example 2 except that the samples were incubated at 120 F. at 50% relative humidity for one week instead of for two weeks. The emulsion was a high speed negative-type gelatino-silver bromoiodide emulsion that was coated at a coverage of 355 mg. of silver and 840 mg. of gelatin per square foot on a cellulose acetate film support. The results are surnarized by the data set out in Table D below wherein the speeds and concentrations are described for Tables A, B, and C.

Table D Original Test 1 Week at 120 1"., Cone. of 50% RH. Addenda Addenda Speed Fog Speed Fog Control 100 15 94 26 Addendum #4. .09 102 13 S9 21 Do 45 94 12 l8 Addendum #10 003 14 94 21 o .03 112 .13 100 .17

Control 100 21 68 38 Addendum #11 12 85 22 73 27 Addendum #12 12 83 21 74 .25

100 17 58 52 .003 16 68 42 Do r. .03 83 .16 65 .27 Addendum #14 .3 97 16 57 .44

Control 100 11 76 28 Addendum #15 .09 78 12 78 .14

EXAMPLE 4 Example 3 was repeated with two additional addenda of the invention except that the incubation period was two weeks instead of one week.

The addenda of the invention can also be utilized as built-in fixers for photographic silver halide emulsions when utilized in amounts of at least about equal to the silver halide in the emulsion on a molar basis. Such is illustrated by Examples 5 and 6 below.

EXAMPLE 5 To a photographic gelatino-silver bromide high speed negative-type emulsion containing .05 mole of silver bromide per 40 grams of a 6.3% aqueous solution of gelatin was added Addenda #4 in an amount equal to about 1.2 moles thereof per mole of silver bromide which was then coated at a coverage of 10 cc. of the emulsion per 5 inch by 14 inch of surface on a cellulose acetate film support. The resulting film was then exposed through a negative for seconds at 34 inches with a 60 watt light bulb. The film was then developed for 10 minutes at 68 F. in a developer having the formula:

G. Sodium sulfite (anhydrous) 90 Hydroquinone 45 Sodium hydroxide 37 Potassium bromide 30 Water to make one liter.

After a two second water rinse the resulting film was permitted to dry under ordinary room illumination without further processing. The unexposed image areas of the developed film had a slight yellow cast or haze which did not darken upon prolonged exposure to ordinary room illumination.

EXAMPLE 6 Example 5 was repeated except that 2 moles of Addenda #3 per mole of silver bromide were utilized in lieu of Addenda #4. Here again, without a fixing step, the unexposed areas of the developed film had a slight yellow cast which did not darken upon prolonged exposure to ordinary room illumination.

The present invention thus provides new and useful photographic silver halide emulsions, and which emulsions have improved antifoggant properties and self fixing properties.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention described hereinabove and as defined in the appended claims.

We claim:

1. A photographic gelatino-silver halide emulsion containing at least about .001 gram per mole of silver halide of a compound having the formula wherein R is an aryl radical and Z is selected from the group consisting of an aryl radical, an aralkyl radical, a heterocyclic radical, and an alkyl radical containing a substituent selected from the group consisting of a carboxyl radical and a morpholino radical.

2. A photographic gelatino-silver halide emulsion containing at least about .001 gram per mole of silver halide of a compound having the formula wherein R is an aryl radical and Z is selected from the group consisting of an aryl radical, an aralkyl radical, a heterocyclic radical, and an alkyl radical containing a substituent selected from the group consisting of a carboxyl radical and a morpholino radical.

3. A photographic gelatino-silver halide emulsion containing at least about .001 gram per mole of silver halide of a compound having the formula wherein R is an aryl radical.

4. A photographic gelatino-silver halide emulsion containing at least about .001 gram per mole of silver halide of a compound having the formula 0 S-(R) n-HJOII wherein R is an aryl radical, R is an alkylene radical and n is an integer of 1 to 10.

6. A photographic gelatino-silver halide emulsion containing at least about .001 gram per mole of silver halide of a compound having the formula i S(R)ni3OH wherein R is an aryl radical, R is an alkylene radical and n is an integer of l to 10.

7. A photographic gelatino-silver halide emulsion containing at least one mole per mole of silver halide of a compound having the formula 8. A photographic gelatino-silver halide emulsion containing at least one mole per mole of silver halide of a compound having the formula CH 0 I ll S-CHz- O OH 9. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of a compound having the formula 10. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of a compound having the formula S-CHn-(IJ-C CH; 11. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of a compound having the formula OH CH.E-@ -Q 12. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of a compound having the formula 13. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of a compound having the formula l 0 ll wherein R is an aryl radical and Z is selected from the group consisting of an aryl radical, an aralkyl radical, a heterocyclic radical and a substituted alkyl radical.

15. A photographic silver halide emulsion as described in claim 14 wherein the mercapto derivative is present at a concentration of about .001 to 10 grams per mole of silver halide in the emulsion.

16. A photographic silver halide emulsion as described in claim 14 wherein the mercapto derivative is present at a concentration of at least 1 mole per mole of silver halide in the emulsion.

17. A photographic emulsion support having coated thereon a photographic silver halide emulsion as described in claim 14.

18. The process which comprises developing an exposed photographic element as described in claim 17 wherein the emulsion contains at least one mole per mole of silver halide of the mercapto derivative in an aqueous alkaline photographic developing solution and thereby stabilizing unexposed and undeveloped areas of said photographic element.

References Cited in the file of this patent UNITED STATES PATENTS 3,043,690 Green et a1 July 10, 1962 

14. A PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING AT LEAST ABOUT .001 GRAM PER MOLE OF SILVER HALIDE OF A MERCAPTO DERIVATIVE HAVING A FORMULA SELECTED FROM THE GROUP CONSISTING OF 